• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.86-93
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• 1995

An optical transmitter was designed and implemented using a commercially available LiNbO$_{3}$ Mach-Zehnder modulator and the power amplifiers. We have adopted a new method to stabilize the bias voltage of the modulator using the second order harmonic component of the dithering signal. This technique has been applied successfully to the 2.5 Gbit/s external modulator for more than 6 hours without bit error rate degradaton. We demonstrated a repeaterless transmission of a 2.5 Gbit/s signal over 150 km nondispersion-shifted fiber using the transmitter. The receiver sensitivity was -34.5 dBm at 10$_{-10}$ bit error rate. No appreciable BER degradation due to fiber dispersion were observed after transmission.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.251-256
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• 1987

The degradation of barium titanate ceramics was studied under the high AC electric field. At 150$^{\circ}C$, life time was measured as a function of grain size, controlled by varying sintering time at 1375$^{\circ}C$ and electrical properties, such as AC conductivity, capacitance and dissipation factor, were measured during degradation process. The life time decreased as grain size increased in the range of 2.44-8.23$\mu\textrm{m}$. The AC conductivity was remained constant and increased suddenly at the last stage of degradation process. The capacitance was slowly decreased and the dissipation factor was slowly increased as the degradaton progressed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.1
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• pp.26-33
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• 2001

The proposed system was composed of pre-processor which was executing binary/high-pass filtering and post-processor which ranged from statistic data to prediction. In post-processor work, step one was filter process of image, step two was image recognition, and step three was destruction degree/time prediction. After these processing, we could predict image of the last destruction timestamp. This research was produced variation value according to growth of tree pattern. This result showed improved correction, when this research was applied image Processing. Pre-processing step of original image had good result binary work after high pas- filter execution. In the case of using partial discharge of the image, our research could predict the last destruction timestamp. By means of experimental data, this prediction system was acquired $\pm$3.2% error range.